The experimental model employs line Ib transplanted leukemia in syngeneic C58/Wm inbred mice. We are developing a computer simulation of the secondary immune response to malignant line Ib cells. The program consists of 3 phases: (1) development of the model; (2) Verification of the modeling approach; and (3) application of the computer simulation technique to an analysis of the immune response to malignant lymphoid cells. We have completed phases (1) and (2) and are determining how thymectomy and splenectomy affect the rate constants for tumor cell kill in the major tissue and blood compartments.